Initially, telecommunication operators provide links to users through Leased Lines. However, when the branches of the users increase, the cost of Leased Lines augments dramatically, and the management difficulty also increases continuously.
Along with the appearance of an Asynchronous Transport Mode (ATM) technique and a Frame Relay (FR) technique, telecommunication operators begin to provide Point-to-Point Layer 2 links to users through virtual circuit. The users then build their own Layer 3 networks thereon to bear data streams, such as Internet Protocol (IP). The links provided by this technique are all Point-to-Point Layer 2 links, and the configurations are rather complex. Especially when a new site is added, the administrator needs to do a lot of configurations.
A technique for providing Private Network (VPN) over IP network is developed to overcome the drawbacks of the above techniques. In this technique, it is convenient to set rates arbitrarily, and configuration is easy. This technique is Multiple Protocol Label Switch (MPLS) VPN. The MPLS based VPN service has two types: one is Layer 3 (L3) MPLS VPN and the other is Layer 2 (L2) MPLS VPN. L2MPLS VPN includes Virtual Private LAN Service (VPLS) and Virtual Leased Line (VLL). VLL is only adapted for Point-to-Point networking application mode, while VPLS is able to implement Multipoint-to-Multipoint VPN networking. VPLS provides a more adaptable solution for the operators that use Point-to-Point L2 VPN Services. In the VPLS intervention, the internal route layers of the users to L3 VPN may be avoided. The operators can manage and operate only one network, while providing a lot of services, such as Best-effort IP Service, L3 VPN, L2 VPN, Traffic Engineering, and Differentiated Service simultaneously on one network. Accordingly, the fee on build, maintenance, and operation is decreased.
VPLS provides a service on a MPLS network that is similar to Local Area Network (LAN) Service. VPLS allows users to access the network and access each other from a plurality of geographical dispersed points simultaneously, just like these points directly access a LAN. VPLS enables the users to extend from LAN to Metropolitan Area Network (MAN), even to Wide Area Network (WAN).
VPLS forwards Ethernet Packets via Medium Access Control (MAC) addresses. For a packet flooding that cannot be addressed with MAC addresses, this packet is forwarded to all of the ports belonging to a LAN, except for the port that receives the packet. When a packet enters a port, the correspondence relationship between the source MAC address of the packet and the entered port is learned. When the MAC address of the received packet is a broadcast address or a multicast address, the packet is flooded to other ports.
VPLS includes a plurality of Provider Edge Devices (PE), which provide one or more Pseudo Wires (PW) to the connected Customer Edges (CE), so that CEs can communicate with each other on VPLS. VPLS emulates a PW as an Ethernet Port, and learns the correspondence relationship between the source MAC address and the PW.
Label Distribute Protocol (LDP) based VPLS (LDP VPLS) is consistent with Pseudo Wire Emulation Edge-to-Edge (PWE3) on building PW signaling, and is substantially the same on forwarding actions. Therefore, the PWE3 and LDP VPLS can intercommunicate when building a PW; that is, a PWE3 instance on a PE can build a PW with a VPLS instance on another PE, so as to implement intercommunication.
However, in VPLS, PW ID is the VPN ID, which is used to identify a VPN. Therefore, all of the PWs in a Virtual Switch Instance (VSI, a VPLS VPN instance on a PE) have the same PW ID. Two PWE3 PWs may not have the same PW ID, especially when the two PWE3s are on the same PE. The PWE3 PWs that have the same package types need to have different PW IDs. Thus, a VSI is not able to access a plurality of PWE3 VLLs with different PW IDs simultaneously. In an existent network that operates PWE3 service, for connecting PWE3 to VPLS, the configuration of PWE3 needs to be modified so as to keep the PW IDs in PWE3 be consistent with the PW IDs in VSI. Since the modification impacts the existent services, even it cannot be realized through reconfiguration.
Additionally, a VPLS VPN is comprised of VSIs on a plurality of PEs, and these VSIs have the same VPN ID. According to the existing solutions, a plurality of PWE3 VLLs that have different PW IDs cannot be connected to one VPLS VPN.
Furthermore, PWEs is Point-to-Point, and connecting one PE with a plurality of other PEs simultaneously cannot be established. Therefore, the full-mesh topology of PEs, which is required by VPLS Service, is not ensured, and a complete VPLS Service cannot be provided.